Most people think that an overwrap is just for use in the winter, I however tend to use mine all year round. The only time I would be tempted to leave it at home would be if I was doing an overnight session and needed to pack and set up quickly.
The reason I use one all year round is for a number of reasons; they stop condensation, keep warmth in during winter, help keep the inside cooler in the warmer months and the main one for me is that I have room to dry a wrap when it gets wet. So to put it bluntly I do not have the room to dry a wet bivvy but I can dry a wet overwrap.
So there you have it, quite simple really and not a reason for everyone to go out and buy a wrap for their bivvy. However the video below should convince you that if you are going to fish through the winter then a wrap is a really good idea. Before anybody says it must be a cheap bivvy, this is one of the top of the range bivvy’s available.
All the best